EFFECT OF RESERVOIR BOTTOM ON EARTHQUAKE RESPONSE OF CONCRETE DAMS

The absorption of hydrodynamic pressure waves at the reservoir bottom has dominant effects on the structural response of the dam when subjec ted to ground motion. In the present study, a model is proposed for th e absorption effects of the reservoir bottom in the earthquake analysi s of darns. The model utilizes the wave reflection coefficient approac h and is based on the solution of the wave equation in a sediment laye r of viscoelastic material with a constant thickness overlying an elas tic, semi-infinite foundation. Numerical studies were conducted to eva luate the effect of the sediment layer thickness and material properti es as well as the effect of reflection of waves from the underlying ro ck. It is shown that the current approach of assuming the wave reflect ion coefficient at the reservoir bottom based on the characteristics o f the sediment material and excluding the effect of the reflected wave s from the underlying rock, may significantly underestimate the seismi c response of the dam. (C) 1997 Elsevier Science Limited.